Electromigration and Thermal Storage Study of Barrierless Co Vias

Abstract

We study the reliability performance in terms of electromigration and thermal storage of barrierless Co vias. While for our reference with Cu filled vias and a TaNCo barrier/liner system we did observe voids in some vias after electromigration, these voids were not observed for the Co vias and thus the studied system is more scalable towards smaller vias. Long thermal storage measurements show more failures in barrierless Co vias. As this problem is linked to a weak Co/dielectric interface and Co/Cu-intermixing, a better adhesion between the Co and the low-k, the use of a non-porous low-k dielectric and the use of a barrier at the via bottom could help to reduce this phenomenon.